1. Field
Disclosed here in is a method to manage the load on an environmental control system. In particular, the utilization of power access points is restricted to manage the load on the environmental control system of a controlled environment, such as the cabin of an airplane.
2. Description of the Related Art
There are environments where the demand for power can exceed a limited available supply. This problem is particularly acute when power supply is transient. For example, aircraft generators driven by engines will often produce power at less than their maximum capability. Load Distribution and Management Systems (LDMSs) can ensure that that power demand does not exceed power supply by allocating power to certain systems and denying it to others.
On aircraft, the use of consumer power outlets and other electronic devices, such as in-flight entertainment systems, can draw significant amounts of power. Such power loads can cause power demand to exceed power supply, especially when an aircraft's power generator is not producing power at its maximum capacity. Systems for managing power in such limited power environments have been previously disclosed. For example, the LDMS disclosed in U.S. Pat. No. 5,754,445, titled “Load Distribution and Management System,” by Jouper et al., manages power on-board aircraft by restricting the power available to passengers for personal electronic devices. The U.S. Pat. No. 5,754,445 is incorporated by reference herein in its entirety.
Analogous problems to those described above occur in situations where environmental control systems (ECSs) are used to control environmental conditions. When an ECS is required to maintain a specific environmental condition in adverse operating conditions, additional loads on the ECS can cause the ECS's capacity to be impermissibly exceeded. For example, an aircraft ECS acting to maintain a stable and acceptable temperature in an aircraft operating in adverse conditions, such as a hot environment, will be stressed by additional thermal loads. Management of ECS loading is advantageous for several reasons. For example, overloading an ECS can damage it. In aircraft, passenger comfort may be adversely affected by an ECS's inability to maintain a reasonable temperature due to the ECS's capacity being exceeding. Federal Aviation Administration regulations also require aircraft cabin environments to be kept within a specified temperature range. Increased temperatures in an aircraft can also lead to the premature failure and operational degradation of various systems.
Installed ECSs possess a maximum capacity, which often corresponds to a worst-case loading scenario. This maximum capacity will typically be an element of an aircraft's initial design, updated with the inclusion or allowance of new systems that will add additional loads to the aircraft's ECS. In such cases the aircraft's ECS must then be re-evaluated and updated to reflect the possibility of additional loads in a worst-case loading scenario. Especially where the additional loads are highly transient, as with the addition of consumer power outlets that may or may not be in use at any given time, the ECS will be oversized during normal operating conditions because it must be capable of handling the more onerous worst-case loading scenario. A disadvantage of this situation is that the size and weight of the ECS, and thus the overall weight of the aircraft and its fuel consumption, are increased, even though these increases provide limited benefit during normal operating conditions.
The use of consumer power outlets and other consumer electronics such as in-flight entertainment devices can place significant additional thermal loads on an aircraft's ECS. As previously explained, an aircraft's ECS must be sized to accommodate the worst-case loading scenario in which all of these electronics are used simultaneously while the ECS is also stressed by other conditions, such as a high ambient temperature. There remains, therefore, a need for a method and system to manage an ECS, so that the size and weight of the ECS may be relatively low, while still maintaining consumer access to power outlets and other electronic devices during normal operating conditions.